1. Field of the Invention
The present invention relates to a disk drive device which performs recording on a disk recording medium such as an optical disk or the like.
2. Description of the Related Art
Recording data on a disk necessitates means for guiding in order to form data tracks, and to this end, grooves are formed beforehand as pre-grooves, with the grooves or lands (portions between grooves with plateau-shaped cross-sectional forms) being used as data tracks.
Also, there is the need to register address information so that data can be recorded on predetermined locations on data tracks, and this address information is recorded by wobbling the grooves or recorded by forming pre-pits on the data tracks.
For example, with DVDs (Digital versatile Disks), DVD-RWs which are phase-change writable disks, and DVD-Rs which are organic dye change write-once type disks, as shown in FIG. 11, wobbling grooves G are formed on the disk as a pre-format, and land pre-pits LPP are formed on the land L portions between the grooves G.
In this case, the reflected light information obtained by the wobbling grooves is used for disk rotation control and generating recording master clocks and so forth, and the land pre-pits are used for determining precise recording positions in increments of bits, and obtaining various types of information regarding the disk such as pre-addresses and the like. That is to say, address indicating physical locations on the disk are recorded as land pre-pits LPP.
Disk drive devices compatible with such disks read out addresses recorded on the disk as land pre-pits LPP for example, while reproducing or recording, and perform various types of control such as confirming the location of the disk that is being recorded to or reproduced from.
However, with disk drive devices, laser irradiation is consecutively performed on a disk at the time of reproducing, at a reproducing power which is comparatively low level, and the data recorded on the tracks and the above-described land pre-pits LPP information and wobbling groove information is read out from the reflected light information thereof.
On the other hand, at the time of recording, there is the need to read out the information of the land pre-pits LPP for address detection, but the laser irradiation at the time of recording is output at a comparatively high recording power for forming pits on the tracks. More specifically, in the case of recording operations on DVD-Rs or DVD-RWs, the recording power and reproducing power is switched over in pulse fashion in the periods for forming data pits on the tracks, and reproducing power is output in periods for not forming data pits.
At the time of such recording operations, reading address information from land pre-pits LPP for example, is difficult.
FIGS. 12 through 14 illustrate an example of a conventional address information detecting method for when recording.
Addresses are basically detected from push-pull signals P/P which are reflected light information. The drawings illustrate a state wherein a laser spot LS is irradiated on a track formed of tracks and lands, with push-pull signals P/P being obtained as the reflected light information of the laser spot LS. Though the drawings omit illustrations of the photo-inductor for detecting the reflected light and the computation circuit, in order to obtain push-pull signals P/P, first, a reflected light amount signal I2 equivalent to the right half of the laser spot LS in the diagram as to the track line, and a reflected light amount signal I1 equivalent to the left half thereof, are extracted as reflected light information.
In the example shown in FIG. 12, the reflected light information signals I1 and I2 are each subjected to decay processing at the attenuators 101 and 102. The attenuators 101 and 102 are supplied with read/write signals for distinguishing between recording operations and reproducing operations, and are controlled to execute decay processing only during recording operation.
Accordingly, while reproducing, decay is not performed by the attenuators 101 and 102, so the reflected light information signals I1 and I2 are in that state subjected to subtraction of I1 minus I2 at a subtracter 103, to form a push-pull signal P/P. While recording, the reflected light information signals I1 and I2 are subjected to decay processing at the attenuators 101 and 102 and then subjected to subtraction of I1 minus I2 at the subtracter 103, to form a push-pull signal P/P.
Then, the push-pull signal P/P is compared with a predetermined slice level at a comparator 104 and binarized, and taken as the detection information of the land pre-pits LPP. The detected information of the land pre-pits LPP is supplied to a later unshown address decoder, whereby the address value is detected.
However, with the method shown in FIG. 12, the information of the land pre-pits LPP cannot be detected well at the time of recording in actual use, and the address error rate is quite poor.
With the example shown in FIG. 13, the reflected light information signals I1 and I2 are subjected to decay processing at the attenuators 101 and 102 in the same manner as with the above FIG. 12, at the time of recording.
Subsequently, the output of the attenuators 101 and 102 is subjected to addition of I1+I2 at an adder 105, and the addition results are supplied to dividers 106 and 107. Also, the output of the attenuator 101 is supplied to the divider 106, and the output of the attenuator 102 is supplied to the divider 107.
At the divider 106, computation of I1/(I1+I2) is performed, and computation of I2/(I1+I2) is performed at the divider 107. Each of the division results are supplied to the subtracter 103 and subtracted, thereby obtaining a push-pull signal P/P. The push-pull signal P/P is then binarized by the comparator 104, and taken as the detection information of the land pre-pits LPP.
With this method, the address error rate during recording operations are improved over those of the method in FIG. 12, but there is a margin of error in the division processing itself, so the degree of improvement in the error rate is not greatly improved. Also, the dividers 106 and 107 are expensive, so there are difficulties price-wise, as well.
In the example in FIG. 14 as well, the reflected light information signals I1 and I2 are subjected to decay processing at the attenuators 101 and 102, as with the example shown in FIGS. 12 and 13.
However, in this case, AGC circuits 108 and 109 are disposed before the attenuators 101 and 102, so the amplitude levels of the reflected light information signals I1 and I2 are made constant. Other configurations are the same as shown in FIG. 12.
With this method as well, the address error rate during recording operations is improved over that shown in FIG. 12, but the degree of improvement in the error rate is not very great.
Also, combining an AGC circuit such as shown in FIG. 14 with the method shown in FIG. 13 is not a fundamental improvement.
Thus, conventionally, there has been a problem in that detection of address information as information and the like of land pre-pits LPP at the time of recording is difficult.